Heat-developable photographic light-sensitive materials and methods for forming images using such materials are well known, and are described in detail, for example, in Shashin Kogaku no Kiso (Fundamentals of Photographic Engineering), Corona Co., Ltd., pp. 553-555 (1979), Eizo Joho (Image Information) (April 1978), p. 40, and Neblette's Handbook of Photography and Reprography, 7th Ed., Van Nostrand Reinhold Company, pp. 32-33 (1977).
For the formation of color images, various techniques have been proposed, including a method in which couplers are used as dye providing compounds (see U.S. Pat. Nos. 3,531,286, 3,761,270 and 4,021,240, Belgian Pat. No. 802,519, and Research Disclosure (September, 1975), pp. 31-32), a method in which compound with a nitrogen-containing heterocyclic group introduced in the dye portion are used as dye providing compounds (see Research Disclosure (May, 1978), pp. 54-58), a method utilizing the silver dye bleaching process (see Research Disclosure (April, 1976), pp. 30-32, ibid. (December, 1976), pp. 14-15, and U.S. Pat. No. 4,235,957), and a method utilizing leuco dyes (see U.S. Pat. Nos. 3,985,565 and 4,022,617), etc.
These methods, however, have their respective technical disadvantages. Their common disadvantages include that preservability of light-sensitive materials are poor and degradation such as increase in fog, etc., with the lapse of time occurs.
In order to overcome the above problems, a method using reductive dye releasing substances which release hydrophilic dyes is described in Japanese Patent Application (OPI) No. 58543/83 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). According to the method, the technical disadvantages heretofore known are largely overcome.
However, all of the above described methods for forming images using heat development do not include a technique for stopping development and, thus, problems, for example, increase in fog, degradation of color balance, etc., due to excessive development, are inevitable. As a result, it is difficult to consistently obtain stable images.